The invention relates to a method of producing ingots of unalloyed and alloyed steels having an improved primary crystallization, reduced ingot segregation and a reduced content of non-metallic inclusions, wherein, in a known way (German Auslegeschrift No. 1,812,102), molten steel is first poured into the mould, whereupon a slag mixture is supplied onto it and this slag mixture in turn is supplied with energy during the solidification process of the steel in the mould. The energy advantageously corresponds to at least 120 kilowatt-hours per metric ton of ingot weight. For carrying out this method an apparatus can be used in which a top part, with cooled walls which may be inclined, is placed on the mouth of the mould.
When producing large ingots with the help of the above-described method, difficulties may arise in so far as the necessary high energy supplied to the slag cannot be maintained during the total period of solidification. During the solidification of the steel and the cooling-off of the solidified outer skin, a shrinking of the ingot takes place causing the diameter of the ingot to decrease. Thereby a gap is formed between the wall of the mould and the already solidified skin of the ingot, into which gap the liquid slag flows down from the top part. Consequently, the height of the slag bath remaining in the top part decreases and thus there is also a reduction in the electric resistance available for the release of Joule heat; less Joule heat is developed and the process may take an unstable course, which, in turn, leads to the formation of pipes in the ingot head as well as to ingot segregation.